The present invention relates to a data transmitting/receiving method, a data transmission apparatus, a data reception apparatus, a data transmission/reception system, and a medium storing a program to direct a computer to perform all or a part of the function of means provided in each of the above described apparatuses.
In addition, the present invention relates to transmission of AV contents encrypted in different encrypting methods, and reception of the AV contents.
There are two conventional technologies, that is, a first conventional technology, and a second conventional technology, as described below.
First, the first conventional technology is described below. If data is to be provided only for a specific user, means, etc., then a method for preventing other users or means than the specific user or means from accessing the data is used by the transmission side encrypting and transmitting the data, and the reception side decrypting and uses the encrypted data.
The above described method is described below by referring to an example in which data is transmitted and received from an STB (Set Top Box, that is, a satellite broadcast receiver) for satellite broadcast to a VTR device for recording satellite broadcast data. In this method, data is encrypted to record correct satellite broadcast data only in the VTR device registered as a subscriber for recording satellite broadcast.
FIG. 14 shows a configuration of a conventional data transmission and reception system in which an STB for satellite broadcast functions as a data transmission device, and a VTR device functions as a data reception device. The configuration shows only the components relating to the transmission and reception of data between the STB and the VTR device, and reception means, etc. for receiving data from a satellite to the STB, and recording means, etc. for recording data to a recording medium in the VTR device are not shown here. The present system includes: an STB 101 for converting an electric wave received from a satellite into AV data and transmitting the data to a VTR device 102; and the VTR device 102 for recording the AV data transmitted from the STB 101 in the recording medium.
The STB 101 includes: encryption means 111 for periodically or non-periodically updating a work key Kw, performing a first encryption process using the work key Kw on digital data D obtained by converting an electric wave received from a satellite into AV data so that the digital data D can be converted into encrypted digital data Kw (D), and transmitting the result to the VTR device 102; a key encryption means 112 for generating a control key Kc, performing a second encryption process using the control key Kc on the work key Kw so that the work key Kw can be converted into an encrypted work key Kc (Kw), and transmitting the result to the VTR device 102; a transmission side authentication and key exchange means 113 for performing an authentication and key exchange process with the VTR device 102; and a D-I/F (digital interface) 114 for directly transmitting and receiving data to and from a D-I/F 124 of the VTR device 102.
The VTR device 102 includes: the D-I/F 124 for directly transmitting and receiving data to and from the D-I/F 114 of the STB 101; a reception side authentication and key exchange means 123 for performing an authentication and key exchange process with the transmission side authentication and key exchange means 113 of the STB 101; key restoration means 122 for decrypting the encrypted work key Kc (Kw) using the control key Kc obtained through the reception side authentication and key exchange means 123, and restoring the work key Kw; and decryption means 121 for decrypting the encrypted digital data Kw (D) using the work key Kw restored by the key restoration means 122, and restoring the digital data D.
The data transmitted from the STB 101 to the VTR device 102 is the encrypted digital data Kw (D), the encrypted work key Kc (Kw), and the control key Kc. However, since the encrypted digital data Kw (D) and the encrypted work key Kc (Kw) are encrypted data, and the control key Kc is transmitted after the transmission side authentication and key exchange means 113 and the reception side authentication and key exchange means 123 perform an authentication process, the system has high security against the third party who is illegally using data.
Described below is the second conventional technology. As described above, in recent years there has been developed a technology for transmitting AV contents (AV data) such as movies, etc. using a digital signal, and receiving the AV contents.
A transmission device for transmitting such AV contents encrypts AV contents before transmission to protect the AV contents. A reception device receives and decrypts the encrypted AV contents, and displays the AV contents on the monitor.
As described above, the transmission device encrypts the AV contents. However, there are plural types of encrypting methods for encrypting the AV contents. For example, if the reception device is a normal domestic electric appliance such as a television, etc., then a xe2x80x9cbasic encrypting methodxe2x80x9d referred to as a baseline cipher such as M6, Blowfish, etc. is used corresponding to the domestic electric appliance. On the other hand, if, for example, the reception device is an appliance having a high-level arithmetic operations capability such as a personal computer, etc., then an xe2x80x9cextended encrypting methodxe2x80x9d such as DES or the like which is more complicated and has a higher encryption level is used.
As in the conventional technology, the objects of the present invention exist corresponding to each of the first and second conventional technologies. Therefore, the objects are sequentially described below.
First, the object corresponding to the first conventional technology is described below. As described above, the control key Kc is transmitted after being authenticated. However, if the same control key Kc is continuously used, it may probably be decrypted by the third party. Therefore, the system can have higher security by periodically or non-periodically updating the control key Kc. However, since it is necessary to perform the authentication and key exchange process each time the control key Kc is updated, it is strongly demanded to minimize the frequency of the authentication and key exchange process for the purpose of reducing the load onto the system and improving the transmission and reception efficiency.
FIG. 15 shows a relationship between the execution of the control key update process and the authentication and that of key exchange process when the control key is updated by the conventional data transmission and reception system. The horizontal axis indicates the passage of time. The bar in the first row indicates that the STB is transmitting a data signal. The arrow in the second row indicates the range in which the same control key Kc is used. FIG. 15 shows that control key Kc [1] is updated into control key Kc [2]. The bars in the third through fifth rows indicate that the VTR device is in a reception state. The ranges in which the bars are broken indicate that the reception is suspended. The two vertical arrows in the third through fifth rows indicate that the authentication and key exchange process has been performed.
Since the VTR device in case 1 is not suspended after starting the reception, it performs the authentication and key exchange process after starting the reception, and afterwards performs the authentication and key exchange process only when the control key Kc is updated. Since the VTR device in cases 2 and 3 is suspended after starting the reception, it is required to perform the authentication and key exchange process when resuming the reception. Especially, although the VTR device in case 3 is suspended only for a short time without update of the control key Kc when the reception is resumed, the authentication and key exchange process is to be performed again, thereby increasing the total frequency of the authentication and key exchange process to be performed as compared with the other cases.
The present invention has been developed to solve the above described problems of the conventional data transmitting and receiving method, and the conventional data transmission and reception system, and aims at providing a data transmitting and receiving method, a data transmission apparatus, a data reception apparatus, a data transmission and reception system for improving the transmission and reception efficiency by improving the security by updating a control key, and reducing the frequency of the authentication and key exchange process, and a program recording medium storing a program executed to direct a computer to perform all or a part of the function of means provided in each of the above described apparatuses.
The second conventional technology has the following problems. If the transmission device used when the second conventional technology is described is an appliance having a high-level arithmetic operations capability, such as a personal computer or the like, transmitting the AV contents through an IEEE 1394 bus, and the reception device receives the AV contents through the IEEE 1394 bus, and if, as described above, the reception device has a high-level arithmetic operations capability, such as a personal computer or the like, then the reception device can decrypt the AV contents although the transmission device uses the xe2x80x9cextended encrypting methodxe2x80x9d by encrypting and transmitting the AV contents, thereby no problems arise.
However, for example, a normal domestic electric appliance such as a set top box (satellite broadcast receiver) 59 as well as a personal computer 58, that is, a reception device can also be connected to a transmission device 57 through the IEEE 1394 bus as shown in FIG. 16. In this case, assume that the transmission device 57 encrypts and transmits the AV contents in the xe2x80x9cextended encrypting method,xe2x80x9d the personal computer 58 receives and decrypts the AV contents, and the set top box 59 tries to receive and decrypts the AV contents during the transmission. However, since the set top box 59 cannot use the xe2x80x9cextended encrypting method,xe2x80x9d it cannot decrypt the AV contents.
As described above, the present invention aims at providing, in view of the problem that an AV contents reception device which cannot use a first encrypting method cannot decrypt the AV contents when the AV contents transmission device is transmitting the AV contents encrypted in the first encrypting method, an AV contents transmitting method for allowing the AV contents reception device which cannot use the first encrypting method to decrypt the AV contents when the AV contents transmission device is transmitting the AV contents encrypted in the first encrypting method.
The present invention also aims at providing an AV contents transmitting device for allowing the AV contents reception device which cannot use the first encrypting method to decrypt the AV contents when the AV contents encrypted in the first encrypting method is being transmitted.
The present invention further aims at providing an AV contents transmitting method and an AV contents receiving method capable of allowing an AV contents reception device, which is receiving and decrypting the AV contents encrypted in the first encrypting method in addition to an AV contents reception device which cannot use the first encrypting method, to continuously decrypt the AV contents when the above described AV contents transmitting method is used.
Furthermore, the present invention aims at providing an AV contents reception device, provided in addition to an AV contents reception device which cannot use the first encrypting method and which the above described AV contents transmission device tries to allow to decrypt the AV contents, for continuously decrypting the AV contents encrypted in the first encrypting method.
To solve the above-mentioned problems, one aspect of the present invention is a data transmitting and receiving method in which:
on a transmission side, encrypted digital data obtained by performing a first encryption process on digital data using a work key, and an encrypted work key obtained by performing a second encryption process on the work key using a control key, are transmitted, and
on a reception side, the encrypted work key is received and decrypted using the control key obtained by performing an authentication and key exchange process with the transmission side, and the encrypted digital data is received and decrypted using the decrypted work key, thereby obtaining the digital data, characterized in that:
on said transmission side, the control key is periodically or non-periodically updated, an identifier identifying the control key is assigned for each control key; and
on said reception side, when a reception process is suspended and then resumed, it is determined whether or not the control key has been updated while the reception process is being suspended by referring to the identifier transmitted from the transmission side, and, when it is determined that the control key has been updated, the authentication and key exchange process-is performed again, thereby obtaining the updated control key.
Another aspect of the present invention is a data transmission apparatus, characterized by comprising:
encryption means periodically or non-periodically updating/generating a work key, performing a first encryption process on digital data using the work key to convert the digital data into encrypted digital data, and transmitting the encrypted digital data to a data reception apparatus;
a key encryption means periodically or non-periodically updating/generating a control key, performing a second encryption process on the work key using the control key to convert the work key into encrypted work key, and transmitting the encrypted work key to the data reception apparatus;
a transmission side authentication and key exchange means performing an authentication and key exchange process with the data reception apparatus;
identifier generation means generating an identifier identifying the control key; and
identifier transmission means transmitting the identifier to. the data reception apparatus.
Still another aspect of the present invention is a data reception apparatus, characterized by comprising:
a reception side authentication and key exchange means performing an authentication and key exchange process with a data transmission apparatus;
key restoration means restoring a work key by decrypting an encrypted work key converted by performing a second encryption process on the work key using a control key, said restoring process being performed using the control key obtained through said reception side authentication and key exchange means;
decryption means restoring digital data by decrypting encrypted digital data converted by performing a first encryption process on the digital data using the work key, said decrypting process being performed using the work key restored by said key restoration means; and
identifier recognition means determining whether or not the control key has been updated by referring to an identifier identifying the control key transmitted from said data transmission apparatus at least when a reception process is suspended and then resumed, and, when it is determined that the control key has been updated, instructing said reception side authentication and key exchange means to perform again the authentication and key exchange process to obtain the updated control key.
Yet another aspect of the present invention is a data transmission and reception system, characterized by comprising:
a data transmission apparatus according to the present invention and a data reception apparatus according to the present invention.
Still yet another aspect of the present invention is a computer readable program recording medium, characterized by storing a program for directing a computer to perform each function of all or a part of each component of the data transmission apparatus and the data reception apparatus according to the present invention.
A further aspect of the present invention is an AV contents transmitting method, characterized by comprising the step of:
encrypting and transmitting AV contents in a second encryption method which can be used by an AV contents reception apparatus which cannot use a first encrypting method and issues an authentication request when an AV contents transmission apparatus transmits the AV contents encrypted in the first encrypting method using a transmission line.
A still further aspect of the present invention is the AV contents transmitting method, characterized in that when the authentication request is issued, and when there is an AV contents reception apparatus which receives and decrypts AV contents encrypted in the first encrypting method in addition to an AV contents reception apparatus which has issued the authentication request, the AV contents reception apparatus which receives and decrypts the AV contents in the first encrypting method is notified that an encrypting method is switched into the second encrypting method.
A yet further aspect of the present invention is the AV contents transmitting method, characterized in that a notification of switching the encrypting method is given in a predetermined command or is added to the AV contents.
A still yet further aspect of the present invention is the AV contents transmitting method, characterized in that information about what encrypting method is used as the second encrypting method after the switch is given in a predetermined command or is added to the AV contents.
Another aspect of the present invention is the AV contents transmitting method, characterized in that an encryption key or a seed of the encryption key used in the second encrypting method after the switch is given in a predetermined command or is added to the AV contents.
Still another aspect of the present invention is the AV contents transmitting method, characterized in that a switching timing of the encrypting method is an updating timing for an encryption key in the first encrypting method used before the authentication request is issued.
A further aspect of the present invention is the AV contents transmitting method, characterized in that a notification that the encrypting method is to be switched into the second encrypting method, and information about a switching timing of the encrypting method are transmitted to at least the AV contents reception apparatus which receives and decrypts the AV contents encrypted in the first encrypting method.
A still further aspect of the present invention is the AV contents transmitting method, characterized in that:
said AV contents transmission apparatus stores an AV contents reception apparatus which issued the authentication request; and
it is determined whether or not a command requesting an encryption key for decryption of the AV contents or a seed of the encryption key is received from the AV contents reception apparatus, and when the command is not received, the encrypting method is switched from the second encrypting method to the first encrypting method.
A yet further aspect of the present invention is the AV contents transmitting method, characterized in that:
said AV contents transmission apparatus checks the encrypting method available by each of the AV contents reception apparatus which issued the authentication request and the other AV contents reception apparatus; and
when an AV contents reception apparatus transmitting a command requesting an encryption key for decryption of the AV contents and the seed of the encryption key is an AV contents reception apparatus capable of using the first encrypting method, the encrypting method is switched from the second encrypting method to the first encrypting method.
A still further aspect of the present invention is a program recording medium, characterized by storing a program for directing a computer to perform each function of all or a part of each step of the AV contents transmitting method.
Another aspect of the present invention is an AV contents receiving method, characterized by comprising the steps of:
receiving AV contents transmitted from the AV contents transmitting method; and
decrypting the encrypted AV contents based on an encrypting method used when the AV contents are encrypted and using an encryption key used in the encrypting method or a seed of the encryption key.
Still another aspect of the present invention is the AV contents receiving method, characterized in that:
there is information about switching the encrypting method transmitted together with or in the AV contents in the AV contents transmitting method; and
when the information contains none or one of the information about what encrypting method is used after the switch, and the encryption key used in the encrypting method or a seed of the encryption key,
the information about what encrypting method is used after the switch, or the encryption key used in the encrypting method or a seed of the encryption key, whichever is not contained in the information relating to the switch of the encrypting method, is to be transmitted to the AV contents transmission apparatus.
Yet another aspect of the present invention is a program recording medium, characterized by storing a program for directing a computer to perform each function of all or a part of each step of the AV contents receiving method.
Still yet another aspect of the present invention is an AV contents transmission apparatus, characterized by comprising:
encrypting method selection means selecting an encrypting method used when AV contents to be transmitted are encrypted;
encryption key generation means generating an encryption key for encrypting AV contents corresponding to the encrypting method selected by said encrypting method selection means;
encryption means receiving AV contents, also receiving the encryption key from the encryption key generation means, and encrypting the AV contents; and
a transmission side authentication and key exchange means performing an authentication and key exchange process with an AV contents reception apparatus, wherein
when the AV contents reception apparatus is transmitting the AV contents encrypted in the first encrypting method selected by said encrypting method selection means, and when the AV contents reception apparatus which cannot use the first encrypting method issues an authentication request, the transmission side authentication and key exchange means performs an authentication process with the AV contents reception apparatus which issued the authentication request., and
said encrypting method selection means switches the encrypting method into the second encrypting method the AV contents reception apparatus which issued the authentication request can use.
A further aspect of the present invention is the AV contents transmission apparatus, characterized by further comprising an encrypting method notification means issues a notification that the encrypting method is switched into the second encrypting method to an AV contents reception apparatus which is provided in addition to the AV contents reception apparatus which issues an authentication request, and receives and decrypts the AV contents encrypted in the first encrypting method.
A still further aspect of the present invention is the AV contents transmission apparatus, characterized in that;
said encryption key generation means periodically or non-periodically updates the encryption key;
said encrypting method selection means switches the encrypting method into the second encrypting method at a timing of said encryption key generation means updating the encryption key in the first encrypting method.
A yet further aspect of the present invention is the AV contents transmission apparatus, characterized in that
said transmission side authentication and key exchange means stores an AV contents reception apparatus which issued the authentication request, and
it is determined whether or not a command requesting an encryption key for decryption of the AV contents or a seed of the encryption key is received from the AV contents reception apparatus; and
when the command is not received, said encryption key generation means switches the encrypting method from the second encrypting method to the first encrypting method.
A still yet further aspect of the present invention is the AV contents transmission method, characterized in that:
said transmission side authentication and key exchange means checks the encrypting method available by each of the AV contents reception apparatus which issued the authentication request and the other AV contents reception apparatus; and
when an AV contents reception apparatus transmitting a command requesting an encryption key for decryption of the AV contents and the seed of the encryption key is an AV contents reception apparatus capable of using the first encrypting method, said encryption key generation means switches the encrypting method from the second encrypting method to the first encrypting method.
An additional aspect of the present invention is the AV contents reception apparatus, characterized by further comprising:
a reception side authentication and key exchange means performing an authentication and key exchange process with said AV contents reception apparatus;
encrypting method storage means receiving and information about an encrypting method used in encrypting AV contents from said AV contents transmission apparatus; and
decryption means receiving encrypted AV contents from the AV contents transmission apparatus, receiving an encryption key or a seed of the encryption key from said AV contents transmission apparatus, and decrypting the encrypted AV contents using the encryption key of the seed of the encryption key based on the encrypting method stored in said encrypting method storage means.
Still an additional aspect of the present invention is the AV contents reception apparatus, characterized by further comprising:
request means requesting transmitting information such that;
there is information about switching the encrypting method transmitted together with or in the AV contents from the AV contents transmission apparatus, and
when the information contains none or one of the information about what encrypting method is used after the switch, and the encryption key used in the encrypting method or a seed of the encryption key,
the information about what encrypting method is used after the switch, or the encryption key used in the encrypting method or a seed of the encryption key, whichever is not contained in the information is to be transmitted.